example-di.go

// store/rdb/user.go

// User satisfies user store interface
type User struct {
  db *rdb.DB
}

func New(db *rdb.DB) User {
  return &User{db: db}
}

func (u *User) Get(..) {
  ...
}

func (u *User) Save(..) {
  ...
}

func (u *User) Remove(..) {
  ...
}

// api/users.go 
type Users struct {
  userStore users.Store
  ...
}

func New(store users.Store, ...) Users {
  return &Users{userStore: store}
}

func (u *Users) SomeHandler(ctx context.Context) {
  user, err := u.userStore.Get(1) 
  ...
}

// maybe go further also...(I haven't done this yet)
// users/users.go
type User struct {
  store Store 
  Name string 
  ...
}

func (u *User) Get(id uint64) {
  store.Get(id, &u) 
  ...
}

// main.go 
func main() {
  db := rdb.New(...) 
  us := rdb.New(db)
  uc := api.New(us)
  ...
}